Impact of Convective Lifecycles and Associated Dynamic and Physical Structure of Deep Convections on Aerosol Transport and Cloud Microphysics

Aerosol-cloud interaction has implications to both aerosol transport to the upper troposphere (UT) as well as cloud microphysics regulating precipitation processes, and is an important problem for climate studies. The effect of aerosols on cloud microphysics in deep convection is still unknown and analysis of satellite data is needed to validate the currently available model results. We use along-track Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) vertical feature mask data, CloudSat data, and International Satellite Cloud Climatology Project (ISCCP) deep convection tracking data to study the impact of deep convection on the transport of aerosols to the UT over the regions of South Asia (0˚-40˚N, 70˚-100˚E), the Congo (10˚N-10˚S; 10˚W-40˚E), and the Amazon (5˚N-15˚S; 40˚W-80˚W). To minimize misclassification among aerosols and the clouds at the UT, we have only used data with cloud aerosol discrimination (CAD) scores greater than 70 for the period of June 2006 to May 2008, when CloudSat and CALIPSO overlap with the ISCCP deep convection tracking data. We have also used AURA Microwave Limb Sounder carbon monoxide data and Ozone Monitoring Instrument aerosol index daytime data to validate the aerosol detected by CALIPSO. The modern era retrospective – analysis for research and applications is also used to calculate the omega and the wind shear associated with the collocated convections. Our results suggest that active clouds most likely transport aerosols to high altitudes, whereas decaying clouds are least likely to transport aerosols to the UT. Mature clouds act in-between the active and decaying clouds. Lifecycle and continental differences in cloud fields such as cloud water path (CWP), cloud water content at 10 km altitude, and cloud system radius (CSRAD), as well as dynamic structures like convective system fraction, zonal wind shear, omega, and the number of convective cores (NCC) play significant roles in aerosol transportation. Rain rate, measured from Tropical Rainfall Measuring Mission under the collocated convections, suggests a strong relation with the continental differences in aerosol transportation, which suggests that scavenging effects are also important along with the convective dynamics.

Unlike other clouds types, deep convections are stronger and more vigorous; hence we expect that the aerosol impact on the cloud effective radius (R_e) could be modulated by the cloud dynamics and the physical structure of the deep convections. R_e measured from the Moderate Resolution Imaging Spectroradiometer (MODIS), on board the A-Train satellite AQUA, has been used along with other A Train and collocated ISCCP data to answer this question. Our analysis over the regions indicates that R_e is affected by the aerosol as well as the cloud dynamic and physical structures, and R_e is strongly correlated to the altitudes that the aerosols were transported to. Active convections have the strongest relation to the aerosols (correlation coefficient, 0.62) probably because they tend to transport more aerosols through their updraft than any other stages. Conversely, R_e is intrinsically related to convective parameters such as NCC, Cloud top height, CSRAD, and CWP, however, that dependency weakens from active to decaying convections.